CVE-2024-35873

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

riscv: Fix vector state restore in rt_sigreturn()

The RISC-V Vector specification states in "Appendix D: Calling

Convention for Vector State" [1] that "Executing a system call causes

all caller-saved vector registers (v0-v31, vl, vtype) and vstart to

become unspecified.". In the RISC-V kernel this is called "discarding

the vstate".

Returning from a signal handler via the rt_sigreturn() syscall, vector

discard is also performed. However, this is not an issue since the

vector state should be restored from the sigcontext, and therefore not

care about the vector discard.

The "live state" is the actual vector register in the running context,

and the "vstate" is the vector state of the task. A dirty live state,

means that the vstate and live state are not in synch.

When vectorized user_from_copy() was introduced, an bug sneaked in at

the restoration code, related to the discard of the live state.

An example when this g

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References